研究了高取代度的羧甲基纤维素（CMC）取代度的紫外光谱测定方法.首先利用CMC与Cu（Ⅱ）反应,得到CMC-Cu（Ⅱ）溶液的紫外吸光值随稀硫酸铜溶液体积的变化曲线,发现该曲线可划分为3个区,其中Ⅰ区是CMC链上的羧基与Cu（Ⅱ）离子按照化学计量反应生成配合物的区域,且符合Lambert-Beer定律.将Ⅰ区曲线拟合得到一条直线,当相关系数达0.990时,可通过该曲线与拟合直线的吸光值最大处交点所对应的硫酸铜溶液体积计算得到CMC的取代度.该方法对于取代度大于0.80的CMC具有高的取代度测量准确性,测定结果与国标方法误差在1.7%～3.5%之间,且具有样品用量少、简单、快速的特点.

Proposed in this paper is a UV-based method to rapidly determine the degree of substitution（DS） of carboxymethyl cellulose（CMC） with high substitution.In this method,a curve of the UV absorbance of CMC-Cu（Ⅱ） solution versus the volume of dilute copper sulfate solution is obtained via the reaction CMC and Cu（Ⅱ）,which is divided into three regions,of which regionⅠ defined by Lambert-Beer＇s law corresponds to the stoichiometrical reaction of the carboxyl groups on CMC chain with Cu（Ⅱ） ions.Then,by fitting the curve in region Ⅰ,a straight line is obtained.When the square of correlation coefficient is more than 0.990,the DS of CMC can be calculated according to the volume of dilute copper sulfate solution at the intersection with maximum absorbance.The proposed method,which is of the advantages of rapidity,simplicity and is of small quantity of sample involved,is accurate in determining the DS of CMC with a DS higher than 0.80.As compared with the national standard method,the error of the proposed method ranges from 1.7% to 3.5% only.